Angle converter



1.1. F. BLACKBURN ANGLE CONVERTER Aug 25, 1964 4 Sheets-Sheet 1 Filed March 29, 1949 XOM JE-ZONEOI mum I II III IIIIIIIIIIIIIIIN JOHN E BLEEFFfil/RN I J. F. BLACKBURN Aug; 25, 1964 ANGLE CONVERTER 4 Sheets-Sheet 2 Filed March 29, 1949 Aug. 25, 1964 J, F. BLACKBURN ANGLE CONVERTER 4 Sheets-Sheet 3- Filed March 29, 1949 mr w wa m2:

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lllllllllL j l l l I l l i 4 l I JOHN E BLACKBURN Mowing United States Patent 3,146,443 ANGLE CGNVERTER John F. Blackburn, Belmont, Mass, assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Mar. 29, 1949, Ser. No. 84,028 (Ilaims. (Cl. 343-4) This invention relates to improvements in ordnance apparatus and more particularly to an improved angle converter suitable for use in naval gun fire control apparatus.

In prior art gun order converter apparatus for use on board a vessel, it has been the usual practice to employ elaborate, complicated, and expensive servo systems to compensate" for the aforesaid vessels roll and pitch and continuously maintain the gun trained to fire at the target.

In accordance with a preferred embodiment of the instant invention, the apparatus required for compensating for'the roll and pitch is incorporated in the angle converter and none of the aforesaid servo mechanisms are required. The apparatus of the instant invention performs all of the functions, possesses all the advantages and none of the disadvantages of prior art devices and is simple in operation in contradistinction to prior art devices. Preferably, it includes a pair of rectangular potentiometer windings which are secured to a rotatable support card in mutually perpendicular positions thereon. The support is continuously positioned in accordance with the deck train and deck elevation of the director as the director is automatically positioned to maintain the line of sight thereof substantially on the moving target, so that the axis of rotation of the card is continuously maintained substantially along the line of sight.

A movable finger is provided on which the movable arms associated with both of the aforementioned potentiometer windings are mounted in a manner to maintain the arms extending in mutually perpendicular directions. The finger is positioned in accordance with the lead angles of the target so that it substantially coincides with the desired gun pointing. The voltages derived from the potentiometers are employed for obtaining error signals in a pair of electrical servo loops. The card upon which the potentiometers are mounted is continually rotated through an angle corresponding to the rotation of the vesselabout the line of sight between director and target as a result of roll and pitch, thereby stabilizing the gun fire control system against the introduction of substantial errors as a result of the departure of the deck or other structure upon which the director is mounted from a true horizontal position.

A pair of dilferential devices, such for example, as differential gears, each of which has a deck input and a lead angle input, supply gun orders in train and elevation.

One of the objects of the invention is to provide new and improved angle converter apparatus which is reliable in operation and which possesses the desired qualities of ruggedness, durability in service, and a high degree of accuracy.

Another object is to provide new and improved angle converter apparatus suitable for use aboard a vessel and in which rotation of the deck around the line of sight of the director resulting from roll and pitch of the vessel is compensated for in a simple and inexpensive manner.

A further object is toprovide a new and improved angle converter apparatus suitable for use on a vessel and in which gun orders are constantly and substantially instantaneously corrected to compensate for movements of the vessel resulting from roll and pitch.

Other objects and manyof the attendant advantages of the instant invention will be more clearly apparent from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a geometricaldiagram illustrating the operation of the device embodying the instant invention according to the preferred embodiment thereof;

FIG. 2 is a schematic diagram of a system comprising a circuit and apparatus suitable for use with the present invention;

FIG. 3 is a view in elevation of the mechanism for positioning the otentiometers, and associated apparatus of FIG. 2; and

FIG. 4 is an alternative form of the invention employing the device of FIG. 2.

In describing the operation of the apparatus, the following nomenclature is employed:

Line of sightThe line corresponding to the direction in which a gun director on the ship is pointing or sighting. In the following description it is assumed that this director is pointing toward the present or instant position of the target.

Gun axis-The axis of the gun bore corresponding to the instantaneous pointing of the gun.

Correct gun pointingThe direction in which it is desired to point the gun in order that the target may be hit.

TraverseThe angle intercepted at the director by a vector representing the horizontal component of. displacement of the target. This angle is measured in a plane containing the line of sight and a horizontal line perpendicular to the line of sight.

Gun deck trainThe angle between the fore and aft axis of own ship and a plane through the-gun axis perpendicular to the deck, measured in the deck plane, clockwise from the bow of the vessel.

True elevation angle-The angle representingv the elevation above the horizontal plane of the line of sight, measured in the vertical plane through the line of sight.

Deck elevation angle--Angle between the line of sight and the deck, measured in a plane perpendicular to the deck and passing through the line of sight.

True coordinates-The coordinate relative to the true north-south line, the horizon and the vertical at the position of the ship.

Deck coordinates The coordinate system with reference to the plane of the deck and fore-aft axis of the ship.

Computed lead angleThe angular diiference between the line of sight and the correct gun pointing from the position of the director. It may be expressed in either true or deck coordinates.

Actual lead angle-The angular diiference between the line of sight and the gun axis and is the computed lead angle corrected for parallax. It also may be expressed in true or deck coordinates.

EZ7-Deck elevation of line of sight.

EgDeck elevation of gun axis.

Br'Deck train of line of sight.

D'd--The deck train component of the actual lead angle.

B'grTotal actual decktrain angle of gun axis. This equals Br'-+D'd.

U-Average velocity of projectile during'its flight to target.

Zs-Cross traverse; that is, angular rotation of ship about the line of sight due to roll and pitch.

dBs-Rate of change of traverse angle with respect to time, resulting from the motion of the target.

dE-Rate of change of elevation angle With respect to time, resulting from motion of the target.

R-Range of target.

RdBs-This equals the horizontal component of the tangential velocity of the target.

Ra'EThis equals the elevation component of tangential velocity of the target.

VVertical deflection angle: The angle between the line of sight and the plane through the gun perpendicular to the vertical plane through the line of sight measured in the vertical plane through the line of sight and of positive sign when the gun is above the line of sight.

VdElevation dilference: Algebraic difference between gun elevation and director elevation.

e-Placed before any quantity means error in that quantity, for example: eV and eD are voltage proportioned to the error signal for V and D.

d-After a quantity indicates that the quantity is measured with reference to the deck.

g-After a quantity indicates that the quantity is in reference to the gun.

A prime after a basic symbol indicates that the quantity is measured in the plane of the deck of our own ship or is a plane perpendicular to the deck of our own ship.

Referring now to the drawings in which like reference characters are used throughout to designate like parts for a more complete understanding of this invention, and more particularly to FIG. 2 thereof, there is generally shown at 11 a fire control director and radar. This fire control director may be conveniently rotatably mounted upon the deck of the vessel and movable in train, hereinbefore designated by the quantity Br'. Included in this director is a movably mounted radar antenna system rotatable in elevation, which elevation is measured with respect to the deck in the aforedefined quantity E'b. The director also contains suitable apparatus including, for example, a suitably mounted gyroscope stabilized to maintain a vertical spin axis, and pick-off transformer for measuring the rotation of the ship about the line of sight in an amount Zs, as the ship rolls and pitches. The director and radar equipment provide an arrangement for automatically tracking the target. The director and radar 11 also provide means including, for example, a precessable line of sight gyroscope, for measuring the angular rates of motion of the target in a pair of mutually perpendicular planes in elevation and transverse respectively, and deriving signals or currents therefrom which are proportional to the quantities dB and dBs respectively. Apparatus 11 also includes means for multiplying these dB and dBs signals by the quantity R to obtain two linear rate voltages or signals RdE and RdBs respectively.

A director and radar arrangement such as that shown and described in the copending application of Ivan A. Getting for Gun Fire Control System, Ser. No. 61,558, filed November 23, 1948, is especially suitable for use with the instant invention.

Reference is made now to FIG. 1 in which is shown a geometrical diagram of the angular and motion relationships of the target fire control system as represented by the various signals employed in the angle converter.

As stated hereinbefore, in the instant invention the line of sight is maintained substantially on the target by radar controlled means. The computed lead angle is ascertained from signal data as to the velocity of the target. The components of the computed lead angle are added to the coordinates which determine the line of sight and the result is the correct gun pointing.

Date defining the computed lead angle is supplied to the system shown in FIIG. 2 in true coordinates. Data defining the line of sight is supplied in deck coordinates. The instant apparatus utilizes these data to provide shaft rotations or settings corresponding to the correct gun pointing.

As aforementioned, the component lead angles are supplied to the angle converter system in terms of RdBs and RdE. Except for corrections for gravity drop of the projectile, drift, parallax, wind, etc., the lead angle may be defined as the angle intercepted at the gun director by a vector representing the tangential displacement of the target during the time of flight of the projectile. It therefore follows that:

tangential velocity of target time of flight average velocity of projectile during fiightX time of flight l U Accordingly, RdBs and RdE, which represent the true components of tangential velocity, will define the lead angle, provided the aforedefined quantity U or average shell velocity is known.

In FIG. 2 is shown the apparatus by which the component lead angles are added to the line of sight coordinates in obtaining gun orders. Yoke member 41 is rotated in deck elevation Eb about the axis of shaft 38 by a mechanical coupling 55 to director 11.

Rotatably mounted upon member 41 is a card support 42 upon which are mounted a pair of potentiometer windings 47 and 48 substantially equispaced from the axis of rotation of the card 42 and disposed in mutually perpendicular directions. The arms 51 and 52 associated with windings 47 and 48 respectively are of substantially equal length, are insulated from each other as at 106 and 107, and are operatively connected to and driven by finger 46 in a manner to maintain the arms in a mutually perpendicular arrangement as the finger 46 is moved in a manner to be subsequently described.

Card 42 may be secured to shaft 43 to rotate therewith, the shaft 43 being operatively connected by mechanical coupling 44 to director 11 and positioned or set in accordance with the value of Zs, or the amount of rotation of the ship about the line of sight, which intersects the plane of the card 42 at 10.

As aforementioned, screen 42 is rotatable about the line of sight and the system is arranged whereby it is substantially always stabilized so that potentiometer 47 is horizontal. For clarity in illustration, FIG. 2 is drawn as if the plane of the deck were horizontal. For this reason potentiometers 47 and 48 appear to be tilted, although, as state, potentiometer 47 is maintained parallel with respect to the true horizontal.

The aforementioned finger 46 is fixed at point 8 to shaft 34 for rotation therewith. Shaft 34 is rotatably mounted in journals, not shown, in a pair of spaced supports 31 and 32 which are both fixed to a rotatable plate or gear 28 to rotate therewith. Fixed to shaft 34 to rotate therewith is a bevel gear 35, meshing with bevel gear 36 fixed to shaft 33 to rotate therewith. Shaft or mechanical coupling 33 extends through orifice or aperture 37 in plate 28 and is operatively connected to servo 18 for positioning or setting shaft 34 in accordance with the quantity E'g, for purposes to be hereinafter apparent. Disc or plate 28 may have gear teeth, not shown, which mesh with the teeth of a gear 27 which is operatively connected by shaft or coupling 22 to servo 21 for positioning or setting plate 28 in accordance with the quantity D'd. An arrangement is thus provided in which finger 46 is positioned in accordance with the quantities Eg and Dd, for purposes to be hereinafter more clearly apparent.

The voltages from potentiometers 47 and 48 correspond to the quantities cRdBs Sine lead angle= tangential velocity of target and cRdE

respectively, as will be subsequently apparent, and are taken from them by way of leads 61 and 62 connected to arms51 and52 respectively. These leads 61 and 62 are connected to a pair of multipliers 14 and 15 respectively which also have applied thereto by connection an input corresponding to the average shell velocity U, which may be obtained from a suitable source 16 which may be any convenient computing device suitable for the purpose. The multipliers 14 and 15, which may be, for example, variable resistor elements such as the potentiometers shown at 273 in the Patent 2,433,843 to Hammond et al., which has a voltage proportional to one variable applied across the winding and the second variable is applied to the movable contact to produce a product. These multipliers are constructed and arranged so that the outputs thereof as delivered to leads 67 and 68 respectively are signals representing cRdBs and cRdE respectively.

As aforementioned, the director and radar 11 supplies two voltage signals proportional respectively to the quantities RdBs and RdE. These two voltages are applied to dilferential amplifiers 12 and 13 respectively, to which are also respectively applied by Way of aforementioned leads 67 and 63 the cRdBs and cRdE signals. Amplifiers 12 and 13, each of which, for example, may consist of a potentiometer in which the two incoming signals are combined to produce an algebraic sum which is then amplified, and which have their outputs applied to their respective leads 81 and 82 to represent the differences between the two inputs to each, and to correspond to the quantities eD and eV respectively.

The voltages on leads 81 and 82 are applied to a signal resolver 17 which may be of conventional design such, for example, as that disclosed in Patent 2,608,682 to Herr and which has the control element thereof positioned by coupling 44 from director 11 in accordance with the quantity Zs.

The output of resolver 17 comprises two voltages representative of the quantities eDd and eV'd developed across leads 71 and 72 respectively, and applied to aforementioned servos 21 and 18 respectively, which servos position or set aforementioned shafts or couplings 22 and 33 respectively in accordance with the quantities Dd and E'g.

Shaft 22 is operatively connected to and supplies a Dd input to a differential 23 which also has applied thereto a B'r input from director 11 by way of coupling 24. The differential 23 supplies a gun train output B'gr to coupling 56 for transmission to gun 58.

Shaft 33 is operatively connected to the gun 58 and supplies an E'g input thereto.

sine lead angle= tangential velocity of target is employed. The distancefrom the origin or point 8 to point 9 is taken as unity and point 9 is displaced so that arms 51 and 52 are moved parallel to the horizontal and vertical otentiometers 47 and 48 by an amount proportional to cRdBs and cRdE

6 respectively. It is noted that the sine of the angle 9-3-10 is the tangential component of the velocity-of the target divided by the average shell velocity during travel thereof toward the target, that is, the angle 9-8-10 is the desired lead angle.

The system shown in FIG. 2 is utilized to effect the displacement of point 9 by the desired amount. It is observed that the D.-C. signals representing the computed lead angles, expressed in a true coordinate system, enter the network from the director 11 and are applied to differential amplifiers 12 and 13 in the form of traverse and elevation tangential rates. D.-C. voltages which may be balanced to ground are applied to potentiometers 47 and 48. The voltages from sliders or arms 51 and 52 are an indication of the position of point 9, FIG. 2. Differential amplifiers 12 and 13 may, if desired, be constructed and arranged to convert their D.-C. inputs into AsC. outputs for resolution at 17.

In the operation of the apparatus, the aforementioned servo arrangement tends to position point 9 until sliders 51 and 52 derive signals proportional to cRdBs U and cRdE respectively, which after multiplication by U are substantially equal to the RdBs and RdE signals. If there are difference voltages generated, these resulting generated voltages are compared with the computed voltages representing these quantities. The voltage difference represents the error in the position of point 9, in true coordinates.

Since point 9 is driven by a mechanical system which moves in deck coordinates, this pointing error is converted to deck coordinates by the resolver 17. Servos 18 and 21 position shaft 46 in deck coordinates in a direction which tends to null or reduce the pointing error to zero. Under such a condition of operation, shaft or finger 46 is pointing substantially in the direction of the correct gun pointing. In finding this position, finger 46 will have been turned through an angle proportional to'the lead angle.

In the operation of the above described apparatus, let it be assumed that the target moves in traverse from its previous position. The new quantity of director train Br"is transmitted to differential 23. The angular rate signal dBs also is multiplied by'R in the director to obtain a new linear rate signal RdBs. The new linear rate signal RdBs applied to differential amplifier 12 is no longer equal to the cRdBs signal applied thereto from lead 67, and an eD signal is developed on lead 81 and, after resolution at 17 to bring it into deck coordinates, operates servo 21 and shaft 22 to thereby position finger 46 in a manner which tends to bring the RdBs and cRdBs signals at amplifier'12 into equality. Shaft 22, it is noted, also supplies an input to differential 23, which accordingly supplies a new B'gr gun order to connection 56 and gun Should the target move in elevation, the operation of the elevation channels of the apparatus is similar to that aforedescribed; a new E'b director position is transmitted by coupling 55 to shaft 33, and an eV signal developed across lead 82 positions shaft 33 and finger 46, tending to equalize the RdE and cRdE signals at amplifier 13, and supplies a new E'g gun order to gun 58.

It will be readily understood that if the target moves simultaneously in both traverse and elevation, both servos 18 and 21 are operated to continually position finger 46, and new gun orders in train and elevation are continually provided to the gun.

Should the ship roll or pitch, and some rotation of the deck occur about the line of sight, a new value of Zs or cross-traverse, obtained from the director and applied by way of connection 44, rotates card 42 until the correct nulling voltages are obtained from the potentiometers attached thereto.

It will be obvious to those skilled in the art that, since the apparatus of FIG. 2 is essentially a complex nulling circuit, if desired, the apparatus of FIG. 2 may be modified by the inclusion of an additional differential 54, as shown in FIG. 4. This differential receives as inputs Eg from servo 18 by shaft 33 and Eb from shaft 55 and gives an output for supplying a corrected Eg to the gun 58 and to the gear 36 through shaft 57. In all other respects the operation of the modified apparatus in FIG. 4 is the same as that of the apparatus described for FIG. 2.

Reference is made now to FIG. 3, in which is shown in elevation an angle converter constructed according to the schematic of FIG. 2. The inputs to the apparatus of FIG. 3 are designated by the same reference numerals as the inputs to FIG. 2.

In the operation of the apparatus of FIG. 3, movement of shaft 22 in deck train rotates the finger about an axis perpendicular to the plane of the deck. Assume by way of description the cross-traverse angle is zero and Eb remains constant. No change in gun elevation results. Finger 46 moves the two bails 94 and 95 laterally. Bail 95 rotates on its upper and lower pivots 98 and 99 in gimbal 92 and does not move 92 and its connected potentiometer arm 52 sideways. Bail 94 however does transmit lateral motion through pivots ltltl and 101 and about pivots 1G2 and 103 to bail 93 and its connected potentiometer arm 51, with the result that there is a change in the voltage obtained from potentiometer 47 but not from potentiometer 48.

Assume now by way of description that shafts 38, 22, and 43 remain stationary, and that Zs equals zero. If shaft 33 is rotated, it acts through the gear train shown and causes finger 46 to move selectively up and down, as viewed in FIG. 3. The action upon the gimbals is analagous to that of the previous example, except that in this case bail 94 rotates about pivots 100 and 101 and causes no motion of gimbal 93 and potentiometer arm 51, but bail 95 drives gimbal 92 about its pivots 104 and 105, producing a motion of potentiometer arm 52 and thus changing the voltage picked off of potentiometer 48.

Whereas for clarity of illustration, Zs is shown as zero in which condition the axis through pivots 100 and 101 coincides with the E axis, it will be understood that this is not the case when Zs is not zero. If Zs is not zero, motion of either shaft 33 or shaft 22 will produce motion of both potentiometer arms 51 and 52, the relative magnitudes of the motions being functions of Zs.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent of the United States of America is:

1. Angle converter apparatus suitable for use aboard a vessel comprising, in combination, director means including radar for obtaining two signals representing the linear velocities RdBs and RdE of a real moving target, means operatively connected to said director means and forming a simulated target moving in substantially the same manner as the real target, means operatively connected to said last named means for obtaining two signals cRdBs and cRdE respectively representing the linear velocities of the simulated target, means operatively connected to said last named means and to said director means for comparing the signals representing movement of the real target with the corresponding signals representing movement of the simulated target to obtain two error signals, and means for utilizing the error signals to alter the movement of the simulated target in a manner which tends to & bring it into conformance with the movement of the real target.

2. Angle converter apparatus according to claim 1 including in addition means for utilizing the signals representing movement of the real target and the signals representing movement of the simulated target to derive gun orders in deck train and deck elevation.

3. Angle converter apparatus of the character disclosed for use aboard a vessel comprising, in combination, director means including radar for obtaining two signals corresponding to the linear traverse and linear elevation rates of a moving target in terms of the quantities RdBs and RdE respectively, a pair of potentiometers having the moving contacts thereof operatively connected together, means for taking from said potentiometers a pair of voltages respectively controlled by the positions of the arms thereof, means for multiplying said pair of voltages by a signal representing the average velocity of a projectile in flight from the director to the future position of the target, means for comparing said last named voltages after multiplication with said RdBs and RdE signals to obtain two error signals representing the differences between the two voltages respectively, means for resolving said two error signals by the amount of rotation of the vessel to obtain two signals respectively representative of the error in the elevation lead angle and in the error in the train lead angle in deck coordinates, means for utilizing said last named signals to position the arms of said potentiometers to a setting which tends to reduce said error voltages to zero, and means operatively connected to said last named means and to said director means for obtaining gun orders in deck train and deck elevation.

4. In angle converter apparatus of the character disclosed for use in a gun fire control system aboard a vessel, in combination, means for computing two signals representative of the linear traverse rate and linear elevation rate of a moving target respectively, artificial target means including an artificial target on said apparatus and moving in a manner similar to the movement of the real target, said artificial target means including dual signal generating means for generating two signals corresponding to the movements of the artificial target in a pair of mutually perpendicular planes corresponding to the traverse and elevation planes of the real target respectively, means for comparing the computed signals with the generated signals to obtain two difference signals, means for utilizing the difference signals for altering the generated signals in a manner which tends to maintain the difference signals at zero, and means operatively connected to said last named means for obtaining gun positioning orders in deck train and deck elevation.

5. In angle converter apparatus of the character disclosed for use aboard a vessel, in combination, director means including radar for computing a pair of signals respectively corresponding to the linear elevation rate and the linear traverse rate of a moving target, means in said apparatus forming an artificial target having an instantaneous position corresponding to the position of the real target, means including a pair of potentiometers for generating a pair of signals respectively representative of the linear rates of motion of the artificial target in a pair of mutually perpendicular planes corresponding to the planes of movement of the real target, means for comparing said last named generated signals with said corresponding computed signals, means operatively connected to said last named means for utilizing the differences between the said computed and generated signals for positioning the arms of said potentiometers to settings which tend to maintain said computed and generated signals in substantial equality, and means operatively connected to said last named means and to said director means for obtaining gun orders in deck train and deck elevation.

6. In angle converter apparatus of the character disclosed for use aboard a vessel, in combination, director means including radar for obtaining a pair of signals corresponding respectively to the linear traverse rate and the linear elevation rate of a moving target, target simulating means on said apparatus and including a pair of potentiometers and having applied thereto four inputs corresponding to the deck elevation of the target, the deck train of the target, the deck elevation lead angle of the gun and the deck train lead angle of the gun, all said inputs positioning said simulated target, said last named means being adapted to generate a second pair of signals corresponding respectively to the traverse and elevation signals of the real target, means for multiplying said pair of voltages by the average velocity of the projectile from gun to target to obtain two signals corresponding to the linear traverse rate and the linear elevation rate of the simulated target, means for comparing said pairs of signals, means for utilizing the differences between the last named signals for altering the position of the simulated target in a manner which tends to reduce the differences between the said pairs of signals to zero, and means operatively connected to said last named means for deriving gun orders in deck train and deck elevation.

7. Angle converter apparatus of the character disclosed for use aboard a vessel comprising, in combination, a director including radar, said director being constructed and arranged to provide a pair of output signals corresponding to the linear traverse rate and linear elevation rate of a moving target, a pair of differential amplifiers having said signals applied thereto respectively, means forming a simulated target whose movement is maintained substantially similar to that of the real target, said simulated target means including means for compensating for the roll and pitch of the vessel, means for obtaining a pair of signals corresponding respectively to the linear traverse rate and linear elevation rate of the simulated target, means for applying said last named pair of signals to said differential amplifiers respectively, said differential amplifiers being constructed and arranged to provide output signals representative of the difierences between the signals applied thereto respectively, means for resolving said output signals by a factor corresponding to the amount of rotation of the vessel around the line of sight as a result of roll and pitch of the vessel, servo means having said signals after resolution applied thereto, said servo means being operatively connected to said means for obtaining a pair of signals corresponding to the movements of the simulated target, and means operatively connected to said servo motor and to said means for obtaining a pair of simulated voltages for obtaining a pair of gun orders in deck elevation and deck train.

8. Angle converter apparatus according to claim 6 including in addition means for continuously rotating said potentiometers in an amount corresponding to the rota- 10 tion of the deck of the vessel about the line of sight, thereby to correct said gun orders for said rotation.

9. In angle converter apparatus of the character disclosed for use aboard a vessel in conjunction with a target director and gun fire control system, in combination, a pair of similar potentiometer windings having a pair of movable contact arms associated therewith respectively, said windings being disposed in mutually perpendicular positions, said contact arms being both operatively connected to a movable finger, means for rotating said windings together about a common axis in an amount corresponding to the rotation of the deck of the vessel about the line of sight of the director, means including a plurality of bails pivotally connected together and operatively connected to said director and finger for positioning said finger in accordance with the train lead angle of the target and the deck elevation of the gun, and means operatively connected to said last named means and to said potentiometer windings for continually readjusting the position of said finger as the target moves with respect to line of sight of the director.

10. In angle converter apparatus of the character disclosed for use in a radar controlled gun fire system aboard a vessel and employing a director, in combination, moveable means, a pair of potentiometer windings arranged on said moveable means in mutually quadrature spaced relation for movement therewith, a second moveable means having a pair of contact devices secured thereto for selective electrical engagement with said windings respectively as the second moveable means is moved, a finger for moving said second moveable means, means for moving said first named moveable means by an amount corresponding to the degree of angular movement of said director, a plurality of gimbal elements operatively connected to said finger and director for positioning the finger in accordance with the train lead angle of a target and the deck elevation of the gun, and means operatively connected to said last named means and to said potentiometer windings for continually maintaining the finger in an adjusted position corresponding to the instant position of the target with respect to the line of sight of the director.

References Cited in the file of this patent UNITED STATES PATENTS 1,880,174 Dugan Sept. 27, 1932 1,891,397 Watson Dec. 20, 1932 2,069,417 Murtaugh Feb. 2, 1937 2,339,508 Newell Jan. 18, 1944 2,410,638 Davis NOV. 5, 1946 2,414,108 Knowles Jan. 14, 1947 2,433,843 Hammond Jan. 6, 1948 2,463,687 Gittens Mar. 8, 1949 2,486,781 Gittens Nov. 1, 1949 

4. IN ANGLE CONVERTER APPARATUS OF THE CHARACTER DISCLOSED FOR USE IN A GUN FIRE CONTROL SYSTEM ABOARD A VESSEL, IN COMBINATION, MEANS FOR COMPUTING TWO SIGNALS REPRESENTATIVE OF THE LINEAR TRAVERSE RATE AND LINEAR ELEVATION RATE OF A MOVING TARGET RESPECTIVELY, ARTIFICIAL TARGET MEANS INCLUDING AN ARTIFICIAL TARGET ON SAID APPARATUS AND MOVING IN A MANNER SIMILAR TO THE MOVEMENT OF THE REAL TARGET, SAID ARTIFICIAL TARGET MEANS INCLUDING DUAL SIGNAL GENERATING MEANS FOR GENERATING TWO SIGNALS CORRESPONDING TO THE MOVEMENTS OF THE ARTIFICIAL TARGET IN A PAIR OF MUTUALLY PERPENDICULAR PLANES CORRESPONDING TO THE TRAVERSE AND ELEVATION PLANES OF THE REAL TARGET RESPECTIVELY, MEANS FOR COMPARING THE COMPUTED SIGNALS WITH THE GENERATED SIGNALS TO OBTAIN TWO DIFFERENCE SIGNALS, MEANS FOR UTILIZING THE DIFFERENCE SIGNALS FOR ALTERING THE GENERATED SIGNALS IN A MANNER WHICH TENDS TO MAINTAIN THE DIFFERENCE SIGNALS AT ZERO, AND MEANS OPERATIVELY CONNECTED TO SAID LAST NAMED MEANS FOR OBTAINING GUN POSITIONING ORDERS IN DECK TRAIN AND DECK ELEVATION. 